In order to decrease a leak amount of working fluid which flows from a high pressure side to a low pressure side, a shaft seal mechanism is provided around a rotor of a rotary machine such as a gas turbine or a steam turbine. For example, as an example of the shaft seal mechanism, there is a shaft seal mechanism disclosed in PTL 1 below.
The shaft seal mechanism includes a housing which is provided in the stator side of the rotary machine, and a seal body which is accommodated in the housing. The housing includes an accommodation space inside the outer shell, and an opening of the accommodation space is formed toward the outer circumference of a rotor. The seal body includes thin plate seal pieces.
In the seal body, respective thickness directions of the thin plate seal pieces are toward the circumferential direction of the rotor, and the thin plate seal pieces are overlapped with minute gaps to each other. Each thin plate seal piece is disposed to be inclined so that the radially inward end is positioned so as to be closer to the rotation direction side of the rotor than the radially outward end. Moreover, the radially outward end sides are connected to each other and the radially inward ends become free ends.
In the seal body, the radially outward sides are accommodated and supported in the housing, and the radially inward sides extend from the opening of the housing toward the circumference of the rotor.
In the shaft seal mechanism which is schematically configured as described above, the radially inward side of each thin plate seal piece contacts the rotor when the rotor is stopped. However, if the rotor is rotated, the radially inward side floats from the outer circumference of the rotor due to a dynamic pressure effect generated by rotation of the rotor and does not contact the rotor. Thereby, in the shaft seal mechanism, wear of each thin plate seal piece is suppressed, and service life of the seal is lengthened.
In the shaft seal mechanism disclosed in PTL 1, one end in the axial direction of a fluid low pressure region side of the seal body is covered by a side seal plate of the low pressure side. The other end in the axial direction of a fluid high pressure region side of the seal body is covered by a side seal plate of the high pressure side. Moreover, the radial dimensions of the side seal plate of the low pressure side and the side seal plate of the high pressure side are adjusted, sizes in a downstream side space of the one end in the axial direction and an upstream side space of the other end in the axial direction are defined, and thus, gas pressure distribution of the minute gaps is set so as to assist the floating force due to the above-described dynamic pressure effect.
In the shaft seal mechanism, the seal body or the like is accommodated in the housing with a play, the seal body displaces the accommodation space in the axis direction by differential pressure of the fluid, and the side seal plate of the low pressure side which covers one end of the seal body is pressed to the housing. That is, sizes of the upstream side space and the downstream side space of the above-described seal body are designed on the premise of a state where the side seal plate of the low pressure side is pressed to the housing.